Endoscopic retrograde cholangiopancreatography (ERCP) is difficult to perform in patients with a Billroth II gastrectomy because of anatomical changes. The success rate of ERCP and endoscopic sphincterotomy in patients with a Billroth II gastrectomy is lower than that in patients with normal anatomy. In our case, a 76-year-old man with altered anatomy after a Billroth II gastrectomy underwent cap-assisted forward-viewing endoscopic cholangiopancreatography because of bile duct stones. We successfully performed a fistulotomy followed by large-diameter balloon dilation of the fistulotomy tract for the management of choledocholithiasis in this patient with a history of a Billroth II gastrectomy.